It has been estimated that there are in excess of 915 billion barrels of bitumen in 19 major deposits of what are commonly known as "tar sands," The Major Tar Sand Deposits of the World, Phizackerley and Scott, Panel Discussion No. 13, Topic No. 1, The World Petroleum Congress, Mexico City, Apr. 1967. By 1973, petroleum production had diminished sufficiently with respect to demand to generate a world energy crisis. Currently the United States is virtually totally dependent upon Near Eastern petroleum to meet increases in petroleum demands. Irrespective of the vagaries of international politics, there is an ever increasing demand for petroleum with an ever decreasing availability which threatens a world-wide depression.
There are major tar sand deposits in the following eight nations: Canada, Venezuela, The United States, Malagasy, Albania, Trinidad, Rumania and The U.S.S.R. By far, the greatest deposits are located in the province of Alberta, Canada in an area of approximately 30,000 square miles commonly referred to as the Athabasca Tar Sands.
Tar sand deposits may lie either exposed or covered with an overburden of varying thicknesses up to approximately 3,000 feet. Of the 700 billion barrels of crude oil estimated to lie in the Athabasca fields, approximately 15% is free of overburden. Additionally, substantial deposits exist in Eastern Venezuela, Kentucky and Utah which are also free of overburden and total in the millions of barrels.
The composition of the bitumen which permeates the sand varies specifically with respect to location but have many common characteristics. Merely by way of illustration, the Athabasca tar sands comprise fractions ranging from a totally saturated colorless oil having a molecular weight of 360 to a brown-black solid asphaltene with a molecular weight of approximately 2,500. Additionally, there are oil fractions ranging from totally saturated hydrocarbons through a series containing gradually increasing proportions of aromatics. Athabasca Oil Sands, K. A. Clark, Research Council of Alberta, 1963. The various compositions of most of the significant deposits of tar sands have been published. Encyclopedia of Chemical Technology, Second Edition, Volume 19, page 698.
Unlike crude oil deposits which lie in pools, the bitumen in tar sands are not subject to common well-drilling techniques, although a Frasch Process approach appears viable. The sand appears as a tacky to relatively solid black mass and in some instances relatively hard. There are virtually no deposits of free liquid petroleum.
A typical arrangement of tar sand particles discloses a water envelope proximal to the sand particle containing extremely fine solid particles. The water envelope is covered by a continuous bitumen film which interengages with the bitumen film of adjacent sand particles, to form a cohesive mass generally as illustrated in The Encyclopedia of Chemical Technology, Second Edition, Volume 19, page 693. Thus, the bitumen constituent of the tar sands first must be separated from the sand particles and thereafter refined to produce the various usual petroleum distillate fractions.
Various techniques have been proposed for the recovery of bitumen from tar sands. These techniques involve one of two basic approaches: either the tar sand is mined and transported to a processing plant where the bitumen is extracted or the bitumen is extracted from the sand in situ. Additionally, a wide variety of extractive techniques has been proposed and are summarized in The Encyclopedia of Chemical Technology, Second Edition, Volume 19, pages 699 et seq.
The published literature clearly demonstrates that over a period of approximately 47 years, extensive research has been undertaken to develop an economically efficient method for the recovery of bitumen from tar sands without notable success. By 1963, Dr. K. A. Clark, who by then had spent 43 years researching this problem, settled upon a hot water process combining the use of steam, sodium hydroxide and centrifugal force. The great Canada Oil Sands Limited, a subsidiary of the Sun Oil Company expended approximately $235,000,000 on the development of the Clark process which has not achieved significant commercial success.
Additionally, the Canadian Department of Mines and Technical Surveys developed a pilot plant separation process employing cold water and kerosene as a solvent. The kerosene is used in ratios of one-to-one by weight to the bitumen in the feed while the total water added to the process is 2 to 3 times the weight of the feed. Soda ash and wetting agents were also added.
The first step in the cold water process is disintegration of the sand feed mass in a pebble mill together with water, kerosene and other reagents. The pebble mill effluent is mixed with additional water, and fed to a rake classifier to separate the bulk of the sand from the liquid phase. The liquid phase is thickened to concentrate the oil.
The hot water process of Clark includes a wide variety of extremely complicated control conditions and is effected by variations in the composition of the tar sand, particularly its clay content. It is estimated that the overall efficiency of recovery of the Clark hot water process is no greater than 6 to 8%.
Another hot water process has been tested on a laboratory scale by the United States Bureau of Mines as applied to tar sands found in the United States. This process is distinctly different from the hot water process of Clark because a solvent is employed. In the U.S. process, a 33.degree. API fuel oil containing 20 to 25% by volume aromatics is added as a solvent in one-to-three weight ratio based upon the feed bitumen content. The product of this process closely resembles the product derived from the Canadian Mines Branch cold water process. Additionally, it has been found that tar sands which include relatively large concentrations of iron and calcium salts, such as tar sands found in deposits at Edna, California, cannot be extracted by the Clark or U.S. hot water process.
The principal object of the present invention is to provide an inexpensive, single phase separation process applicable to virtually all tar sands resulting in an economic balance which renders the crude oil or other petroleum fractions recovered thereby economically competitive with other sources of such petroleum products.
Another object of the present invention is to provide a composition for the separation of bitumen from tar sands which is rapidly effective under moderate agitation at reasonably low temperatures resulting in an easily recoverable bituminum bearing fraction.